Mesh networking routes data, voice and instructions between nodes and allows for continuous connections and reconfiguration around blocked paths by “hopping” from one node to another node until a successful connection is established. Even if a node collapses, or a connection is bad, the mesh network still operates whether the network is wireless, wired and software interacted. This allows an inexpensive peer network node to supply back haul services to other nodes in the same network and extend the mesh network by sharing access to a higher cost network infrastructure.
Wireless mesh networking is implemented over a wireless local area network using wireless nodes. This type of mesh network is decentralized and often operates in an ad-hoc manner. The wireless nodes operate as repeaters and transmit data from nearby wireless nodes to other peers, forming a mesh network that can span large distances. In ad-hoc networking, neighbors find another route when a node is dropped. Nodes can be either fixed or mobile, with mobile devices forming a mobile ad-hoc network (MANET) known to those skilled in the art.
The mesh networks use dynamic routing capabilities. A routing algorithm ensures that data takes an appropriate and typically the shortest route to a destination. Some mobile mesh networks could include multiple fixed base stations with “cut through” high bandwidth terrestrial links operating as gateways to fixed base stations or other services, including the Internet. It is possible to extend the mesh network with only a minimal base station infrastructure. There are also many different types of routing protocols that can be used in a mesh network, for example, an Ad-hoc On-Demand Distance Vector (AODV), Dynamic Source Routing (DSR), Optimized Link State Routing protocol (OLSR) and Temporally-Ordered Routing Algorithm (TORR), as non-limiting examples. An example of a MANET using the OLSR protocol is disclosed in commonly assigned U.S. Pat. No. 7,027,409, the disclosure which is hereby incorporated by reference in its entirety.
A multi-hop, ad-hoc wireless data communications network transmits a packet among different intermediate nodes using multiple hops as it traverses the network from a source node to a destination node. In a TDMA mesh network, the channel time slot can be allocated before the node data is transmitted. The channel transmit time is typically allocated in a recurring slot. The channel time typically is segmented into blocks as an epoch and blocks are divided into slots used by nodes to transmit data. If the data is an isochronous stream, the data can be repeatedly generated and presented at the source node for delivery to a destination node. The data is time dependent and is delivered by a specified time.
OLSR is described in Request for Comment (RFC) 3626 by the Internet Society Network working group, the disclosure which is incorporated by reference in its entirety. OLSR is a protocol for a mobile ad-hoc network (MANET) that optimizes a classical link state algorithm for a mobile wireless LAN. It uses multipoint relays (MPR) to forward messages broadcast during a flooding process to reduce message overhead, as compared to a classical flooding mechanism, where every node retransmits each message when it receives the first copy of the message. The link state information is generated only by those nodes selected as a multipoint relay. Another optimization can be acquired by minimizing the number of control messages flooded in a network. Optimization can also occur when a MPR node discloses only links between itself and its MPR selectors. Thus, partial link state information can be distributed throughout the network and used for route calculation. Optimal routes in terms of the number of hops can be provided and are suitable for large and dense networks.
OLSR is table driven and exchanges topology information with other nodes regularly. The MPR are the nodes responsible for forwarding traffic distributed to the entire network. Thus, the MPR can reduce the number of required transmissions and operate as a more efficient mechanism throughout the network. OLSR can work in a distributed manner and does not depend on a central control. Each node can send control messages periodically and there can be some message loss. There is also no requirement for a sequenced delivery of messages.
OLSR and other link-state routing algorithms typically assume a single waveform (also known as physical layers or PHY) is used during their network topology and route discovery process. Different waveforms can have different ranges and potentially different data rate characteristics. It is possible that the network topology and routes discovered by the routing algorithms will be different when using different waveforms. That network topology and routes can vary with waveform is a problem.
OLSR proactively computes connection topology and multi-hop routes in a mobile, ad-hoc, wireless network by exchanging OTA message packets between network nodes. HELLO messages are exchanged among each node's local 1-hop neighbors. This allows the sensing of 1-hop neighborhood link states and the discovery of 1- and 2-hop neighbors. OLSR requires all links used for routing to be bidirectional. Topology control (TC) messages are flooded across a wireless network to disseminate the important parts of each node's neighborhood information (the MPR selector neighbors). OLSR is able to compute a network connectivity model and efficient routes from each node to any other node in the network for both directed and broadcast traffic.
OLSR implicitly assumes all HELLO and topology control over-the-air (OTA) message packets are transmitted using a single waveform or a set of waveforms having identical range (i.e., transmission distance or reach), and therefore, identical connectivity characteristics. The RFC 3626 OLSR standard is able to compute a coherent model of network connectivity.
When multiple waveforms having different range characteristics are used to transfer data in the network, the OLSR routing mechanism breaks down. This occurs because, in general, each different waveform will result in different network connectivity, i.e., which nodes can receive a particular node's transmissions when using that waveform. For example, if node X and node Y establish a link transmitting on waveforms A and B respectively, those waveforms are an intrinsic characteristic of the link. If node X sends a packet to node Y, but uses waveform C to transmit, the OLSR discovered link may not exist using waveform C, possibly due to range or interference differences between waveforms A and C.